Counters 2.1 Accuracy

[Mike Trienis <mi...@orcsol.com>]

Hi All,

I'm fairly new to Cassandra and am planning on using it as a datastore for
an Apache Spark cluster.

The use case is fairly simple, read the raw data and perform aggregates and
push the rolled up data back to Cassandra. The data models will use
counters pretty heavily so I'd like to understand what kind of accuracy
should I expect from Cassandra 2.1 when increment the counters.

   -
   http://www.datastax.com/dev/blog/whats-new-in-cassandra-2-1-a-better-implementation-of-counters

The blog post above states that the new counter implementations are "safer"
although I'm not sure what that means in practice. Will the counters be
99.99% accurate? How often will they be over or under counted?

Thanks, Mike.

Re: Counters 2.1 Accuracy

[Phil Yang <ud...@gmail.com>]

IMO, the main concern of C*'s counter is, it is not idempotent. For
example, if you add a counter and get a timeout error, you can not know
whether it is successful. For non-counter writes, they are idempotent so
you can just retry, but if you retry in counter, there may be a double
write.

2015-06-23 12:23 GMT+08:00 Mike Trienis <mi...@orcsol.com>:

>
> Hi All,
>
> I'm fairly new to Cassandra and am planning on using it as a datastore for
> an Apache Spark cluster.
>
> The use case is fairly simple, read the raw data and perform aggregates
> and push the rolled up data back to Cassandra. The data models will use
> counters pretty heavily so I'd like to understand what kind of accuracy
> should I expect from Cassandra 2.1 when increment the counters.
>
>    -
>    http://www.datastax.com/dev/blog/whats-new-in-cassandra-2-1-a-better-implementation-of-counters
>
> The blog post above states that the new counter implementations are
> "safer" although I'm not sure what that means in practice. Will the
> counters be 99.99% accurate? How often will they be over or under counted?
>
> Thanks, Mike.
>



-- 
Thanks,
Phil Yang